The present invention relates generally to lubrication systems for refrigeration compressors and more specifically to such lubrication systems incorporating two stage lubricant pumps having a venting arrangement for venting of gaseous refrigerant entrained within the lubricant as well as an improved distribution passage vent and filtration means operative to restrict the circulation of foreign particles entrained within the lubricant.
Hermetic refrigeration compressors typically incorporate an outer shell having a lubricant sump in the bottom thereof from which lubricant is pumped to the various bearings via axial and radial passages within a drive shaft. Because the sump and lubricant contained therein is in open communication with the refrigerant, some refrigerant may become intermixed therewith in both liquid and gaseous form. Because this refrigerant is often carried into the lubrication pump and passages during operation thereof, it is desirable to provide means to vent the lubricant passages so as to avoid the potential for insufficient lubrication due to the presence of this refrigerant. However, it is possible for such vent passages to act as pumps should they become primed thus short circuiting the oil flowpath.
In some compressors, particularly variable speed compressors, it is necessary to incorporate a multistage oil pump in order to insure sufficient lubrication of the bearings at slower operating speeds because the oil pump output is proportional to the speed at which the compressor is operating. In such two stage pumps, it is possible for liquid refrigerant to be flashed at the first stage thus forming gaseous bubbles within the pump thus reducing the amount of lubricant which the pump is able to supply. Accordingly, it is desirable to provide means to vent such refrigerant so as to increase the volume of lubricant being supplied by the pump.
A certain amount of foreign particles will inevitably be trapped inside a fully assembled compressor in spite of the best efforts to avoid same. Additionally, as the compressor wears both during initial run in periods as well as during on-going operations, it is possible for further particles to accumulate within the lubricating oil. While it is virtually impossible to completely eliminate the presence of such particles, it is possible and desirable to incorporate means to prevent such circulation of any foreign particles.
The present invention provides a lubrication system which incorporates these various features so as to thereby insure an adequate continuous supply of lubricant irrespective of the operating speed of the compressor while also minimizing the circulation of foreign particles therewith. In order to achieve these objectives, a two stage oil pump is provided which incorporates vent passage means within the first stage to reduce the amount of gaseous refrigerant carried to the second stage and thus assure increased oil flow thereto. Further, a unique anti-syphon venting passage is provided in an upper portion of the crankshaft to further reduce the possibility of refrigerant within the oil preventing adequate lubrication of the various bearing surfaces. Further, a filtering screen is incorporated within the lubricant sump to reduce the possibility of foreign particles being drawn into the pump and circulated to the bearings. These features render the lubrication system of the present invention uniquely well suited for use in variable speed compressors as they combine to assure an adequate supply of lubricant is supplied to the bearing surfaces regardless of the operating speed of the compressor.
Additional advantages and features of the present invention will become apparent from the subsequent description and the appended claims taken in conjunction with the accompanying drawings.